What is the PMC twenty5.21?

The PMC twenty5.21 is the smallest member of the company's new twenty5 range of speakers. This began its development as the replacement for the highly regarded twenty series of speakers. As development progressed, two different influences changed this focus somewhat. The first is that customers continued (and indeed continue) to buy the twenty series with considerable enthusiasm. PMC carefully considered the maxim 'if it ain't broke, don't fix it' and have decided to leave it be with simplified finishes.

At the same time, the other influence was making this decision easier. As work on the prototypes progressed, it became clear to PMC that some additional outlay on the speakers – pushing them up in price slightly – would yield some considerable benefits. As such, the twenty5 series occupies the space between the twenty series and the fact series (the crippling shortage of capital letters at company HQ shows no signs of letting up it seems) and while they look like PMC speakers, they are considerably different to what has gone before.

All this does mean that including a pair of the company's own speaker stands, the twenty5.21 now costs a little over two thousand pounds. Given that this sum buys some rather more dimensionally impressive speakers, it asks the question, can all this new engineering and technology deliver a performance commensurate with the asking price? There's only one way to find out...

Specifications

The twenty5.21 is a two way standmount speaker that contains a single 140mm mid-bass driver and a 27mm tweeter. This is a fairly conventional fitment for a standmount speaker but in this case, they represent something of a departure for the company. The main difference between the twenty5.21 and the twenty21 we reviewed in 2015 is that the mid bass driver moves from a doped paper cone to a glass fibre one – a first in PMC speakers. The reasons for this are that the twenty5 models are doing more with airflow (more of which in a bit) and to take full advantage of this, the driver has to be very light and stiff.

This stiffness is only part of the changes undertaken. The dust cap in the centre of the driver is now inverted to provide a more even connection to the rest of the driver. Having created a cone that can travel further without distortion or break up, PMC has then mated it with a beefed up magnet and voice coil assembly that can provide the necessary grunt to allow this to happen. The driver is dotted with interesting thinking that stems from years of PMC monitors being driven to the edge of detonation around the world. The 'spider' – the device that effectively holds the driver together – also serves as a sort of manual break so if you do attempt to put the driver into space, it will impede your efforts to do so, not unlike a soft clipping circuit on an amp.

Compared to the mid-bass driver, the tweeter has been less heavily revised but still boasts a selection of modifications to improve performance from its ancestor in the twenty series. The most visible of these is a new mounting and guard that serves the dual purpose of making the speaker more toddler proof and acting as a means to better spread the high frequency information. This is partnered with a new crossover that is mounted on an especially thick circuitboard that features very thick copper tracks to avoid loss and resistance build up.

By far the most notable aspect of the crossover's design is that it hands over between the tweeter and mid-bass at an exceptionally low 1.8kHz. This gives the tweeter an enormous amount of work to do but PMC is confident that you'll have no idea that such a crossover is in place when you listen to it. A further revision as part of this process is that the crossover now supports single wiring only – further evidence that bi-wiring is likely to be completely extinct as a practise before the year is out.

Like almost all PMC designs, the twenty5.21 uses a transmission line as a means of bass augmentation and this is where some of the most significant changes have taken place. The company has been heavily involved in the process of studying the airflow through the line and as it exits the speaker has made use of computational flow modelling to do this. In the course of this work, some 'pinch points' in the process were identified – and corrected – but a more interesting phenomenon was observed. Air leaving the transmission line had a habit of spiralling on exit creating the sort of turbulence that can be visibly observed with water and other liquids.

To deal with this, PMC has developed a new port which they've dubbed Laminair. This places a series of laminar airfoils in the mouth of the port. These exhibit minimal drag – laminar flow wings are routinely used on aircraft for this reason – but provide sufficient control on the exiting air that the turbulence is obviated. This in turn allows for the greater excursion of the mid-bass driver to be turned into cleaner low end energy than would otherwise be the case.

All of this is then wrapped in a cabinet that looks similar to previous PMC models and includes the very distinctive 'stagger' to the leading and rear edges to aid with the time alignment of the drivers. It takes more of the measurement data to apply bracing at critical points and better isolate the drivers from the outside world. The result is a speaker that is extremely inert considering the small size.

Design

The twenty5.21 is an interesting object to spend a little time studying because while it has many features that mean it could only be a PMC speaker, it also looks different to previous models. The increased brightwork has been added in such a way as to make the speaker more visually interesting but not overly fussy and standard refinements like magnetic grill tabs reduce the number of piercings in the fascia. If anything, the back is even more striking with its mirrored finish (that attracts fingerprints with astonishing vigour).

The virtues we associate with PMC are all present though. This is a solidly assembled speaker that feels like it is comprised of components that are going to stand up to a long life – evidenced in part by the extraordinary 20 year warranty offered on them. This is a product that – although it could never be called cheap – does at least demonstrate where the money has gone. I can't pretend to be hugely fond of the Amarone wood finish but others are available and the veneering itself is of a very high quality.

This is a product that could never be called cheap but does at least demonstrate where the money has gone

How was the twenty5.21 tested?

PMC supplied a pair of their own stands to use with the twenty5.21 and these were used throughout. The PMCs have been tested with a Naim Supernait 2 integrated amp, used with Naim ND5 XS streamer and XP5 XS power supply all connected to an Isotek Evo 3 Sigmas mains conditioner. Some additional testing has been undertaken with an Avid Ingenium Twin turntable and Cyrus Phono Signature phono stage. As such, material used has been lossless and high res FLAC, DSD and AIFF files, streaming material from Tidal and internet radio and a smattering of vinyl.

Sound Quality

Before anything is said about the performance of the twenty5.21, it is important to stress that even more so than most standmount speakers, positioning relative to you is everything. If you simply have them firing straight ahead, they won't deliver anything of what they promise and mild toe-in won't really improve matters. Only when you have the speakers crossing over roughly a metre behind your head will the PMC suddenly 'click' and the comments made henceforth make any sense. In other regards, the twenty5.21 is usefully benign. It has little problem with rear and side walls and the performance is relatively consistent even if your ear is above or below the tweeter line. Without that toe in though, nothing will work.

Follow this simple, basic instruction though and the PMC will show you a few things. The first is that – for reasons I'll expand on – this is a significant step forward over the twenty series. The second is that the revisions to the transmission line have further bent the laws of physics and put the twenty5.21 in a unique place in performance terms. PMC standmounts have always had superb bass for their size. Where the immutable laws of space and time caught up with them was that on occasions, there would be the slightest sense of sluggishness to the end of some really low notes.

It seems that this sluggishness was the audible effect of the turbulent air at the mouth of the port. The revisions made to the twenty5.21 have resulted in a speaker that still hits far harder than a cabinet of this size has any right to but now does so with an immediacy and agility that moves this speaker on from its predecessors. The potent bassline of Public Service Broadcasting's Korolev is reproduced with real force and drive but still possessing the sheer energy that standmounts excel at.

If this was the summation of PMC's achievements with the twenty5.21, it would still be fairly impressive – this is after all, a standmount speaker that can trade blows with small floor standers – but there is more to the work that PMC has carried out with this speaker and these changes don't need bass to make themselves felt. That exceptionally low crossover between the drivers does genuinely work. Detecting where one driver ends and the other begins is a fool's errand and even listening to the live performance of Dead Can Dance' The Wind That Shook the Barley which is all over this 1.8kHz point yields no sign of an audible handover. Perhaps even more importantly, there is a tonal sweetness to the twenty5.21 that wasn't necessarily present with earlier PMCs. This hasn't been bought at the expense of accuracy but there is a smoothness and inviting richness to the way that this speaker makes music that is hard not to be bowled over by. Listening to the rather prog rock esque Ghosts of Pripyat is a deeply impressive experience with considerable dynamics blended into a refinement and control that goes a long way to demonstrating where the money has gone. This is a supremely assured loudspeaker.

Perhaps just as importantly though, it still knows how to engage and have some fun. Listening to Wild Beast's He the Colossus on these speakers is sheer brilliance. The low end punch combined with the effortless cohesion top to bottom ensure that this is a tremendously engaging speaker to listen to. Using them with the Naim electronics that are resident here makes for an excellent partnership but the behaviour of the PMC does suggest that these aren't a quick fix to cover substandard electronics. PMC has done a commendable job in terms of the sensitivity and overall behaviour of the twenty5.21 but they are revealing enough to show up the flaws or quirks in your source equipment and will require a reasonable if not excessive amount of power to show what they can do.

Otherwise, the only real stumbling block to the twenty5.21 is that talented competition surrounds – and in one or two cases slightly undercuts – it. With the PMC stands added to the £1,870 asking price, this is a £2,000 speaker system and if you have a larger room especially, there are floorstanding options that will keep the twenty5.21 honest. Having spent some time with the PMC though, if this were my budget for speakers and I was choosing for this normal sized lounge, few other models I've tried at this price point have the sheer ability and 'rightness' in this room and I suspect that this is not some isolated event.

Perhaps just as importantly though, it still knows how to engage and have some fun

Conclusion

PMC twenty5.21 Speaker Review

The PMCs went through the review process at the same time as the Mission LX-2, a speaker that you can have 11 pairs of for the price of the twenty5.21. Having the two speakers side-by-side has been illuminating. The PMC isn't 11 times as good – it might not actually qualify as twice as good such is the law of diminishing returns. What the PMC does is sound bigger, fuller and just more together than a speaker of this size possibly should. This is PMC at their best and the result is a speaker that comes Highly Recommended.